This invention relates to a rotor of induction motor having no winding slots in its outer circumferential surface.
In recent years, as this type of rotor of induction motor, a rotor has been proposed in which on the outer circumferential surface of a rotor core, a conductive cover is provided which is made of a complex material of magnetic and electrically conductive materials, thereby ensuring that vibration and noise can be reduced and electrical characteristics such as torque characteristics can be improved (See U.S. Pat. No. 4,409,506, for example).
In the known rotor of induction motor, however, a loss due to spatial higher harmonics magnetic flux of higher order generated by a pulsating magnetic flux at stator slots was not taken into consideration. More particularly, the magnetic force is intensified at teeth but weakened at slots of the core of the stator and as a result eddy currents are generated in the circumferential surface of the rotor, giving rise to torque loss and heat loss.